With the advent of sophisticated computers, facsimile machines, printers, and other computer-related electronics equipment, the need for external printed circuit (PC) interface to be used by the computer and computer-related equipment is ever increasing. To this end, PC cards containing external memory and data to be used in computer processes have been designed. At the present time, there are three different PC card types, as defined by the Personal Computer Memory Card International Association (PCMCIA). This is the standards body responsible for developing the 68-pin PC card standard. The three PC card types, are as follows:
a. Type I PC Cards are the same width and length as a common credit card, 54 mm.times.85.6 mm, but are thicker than a credit card. The thickness of a Type I card is 3.3 mm (0.130").
b. Type II PC Cards are used by those companies which are utilizing memory components that are too high to be housed within a Type I card. Type II memory cards are also the same overall length and width as credit cards, but have raised body cross section in the substrate area which gives them an overall thickness of 5 mm (0.195"). The raised substrate areas of these cards are 48 mm in width.
c. Type III PC Cards are the result of a recent movement sponsored by the Small Form Factor Committee (SFF) to enable 1.8" Small Form Factor Disk Drives to be plugged into memory card connectors in small portable computer applications. Type III PC cards are the same length and width as Type I and Type II PC cards. However, Type III cards have a substrate area thickness of 10.5 mm. Also, Type III PC cards require a card guide opening width of 51 mm of the header connector to accommodate the slightly raised substrate area.
PC cards generally comprise a printed circuit board, a casing made of an insulting material for housing the printed circuit board, and at least one connector, typically referred to as an "I/O" connector. The connector is provided on one end of the casing for interfacing the memory card, and particularly the printed circuit board contained in the casing, to the computer equipment to which the card is mated. The connector is designed to extract the contents of the memory stored on the printed circuit board and to bus data to and from an outside environment, which also usually comprises a computer or other electronic equipment. In this fashion, data traverses the interface between the PC card and the outside environment so that the data can be efficiently transferred and used by the computer to which the card is mated for its intended purpose.
PC cards are generally interchangeable and can be used with many different machines and electronic components. Because the PC cards are interchangeable, they undergo a significant amount of abuse when transported, interfaced and mated to the different computers and electronic equipment which use them. Since a PC card is conventionally made up of a number of layers and/or elements glued or otherwise bonded together, the individual layers tend to become loose and/or separated from one another as the memory card is subject to flexing stress, as typically occurs when the card is inserted into or removed from the electronic or other computer-type equipment. Thus, even after moderate amounts of usage, conventional memory cards have heretofore frequently become structurally loose, and the internal members of the card often become misaligned. This results in failure of the PC card and degrades the performance of the electronic equipment which uses the card. These undesirable results generally induce poor performance of the computer system which uses the memory card.
Another undesirable result which induces poor performance of the computer system results from inadequate shielding of the PC card and the connectors electrically connected thereto. In the prior art, PC cards had separate shields which were provided proximate the various components of the card. This discontinuous shielding provided breaks in the shielding and limited the effectiveness of the memory card, particularly in environments in which many electronic devices were located. Notwithstanding the above, U.S. Pat. No. 5,005,106 teaches a system for providing continuous shielding to a substrate. Specifically, the patent teaches the use of a flexible, conductive envelope into which the substrate may be inserted, then placed within an insulative housing.
The present invention avoids these undesirable results or complexities by the provision of a continuous shielding arrangement that is easy to assemble. The uniqueness of this arrangement will become apparent from the description which follows, particularly when read in conjunction with the accompanying drawings.